1. Technology Field
The present invention generally relates to a storage apparatus, in particular, to a storage apparatus having a plurality of storage modes, a flash memory controller, and a switching method thereof.
2. Description of Related Art
Along with the widespread of digital cameras, camera phones, and MP3 in recently years, the consumers' demand to storage media has increased drastically too. Flash memory is one of the most adaptable memories for such battery-powered portable products due to its characteristics such as data non-volatility, low power consumption, small volume, and non-mechanical structure. Besides being applied in foregoing portable products, flash memory is also broadly applied to external products such as flash cards and flash disks. Thereby, flash memory has become one of the most focused electronic products in recent years.
A flash disk usually uses a control IC and a flash memory to communicate with a personal computer (PC) through a data transmission interface. The most commonly adopted data transmission interface is universal serial bus (USB). Due to the characteristics of USB transmission interfaces, flash disks offer plug-and-play and hot plugging functions. Besides, since most existing PCs come with USB interfaces, the application range of flash disks is greatly increased. When a user want to access data in a PC through a flash disk, the user does not have to re-start the PC as what he/she would do when the hardware configuration of the PC is changed. In other words, once the USB plug of a flash disk is plugged into a host computer, the operating system in the host computer instantly assigns a slot as the space for accessing the flash disk so that data can be directly accessed. From users' point of view, flash disks provide a lot of convenience. Moreover, a flash disk is usually designed very light, slim, and small but at the same time has a large storage capacity and can be read or written repeatedly. Thereby, flash disk has become the mainstream in today's storage media market.
Flash memories in flash disks can be categorized into single level cell (SLC) NAND flash memories and multi level cell (MLC) NAND flash memories according to the memory cells thereof. Due to the physical characteristics of MLC NAND flash memory, charges in some pages are not very stable and which may affect the adjacent pages. Accordingly, the reliability of MLC NAND flash memory is not very satisfactory even though it can provide a large storage capacity. Contrarily, the speed and durability of a SLC NAND flash memory are both better than those of a MLC NAND flash memory, but a SLC NAND flash memory offers a smaller storage capacity than a MLC NAND flash memory with the same chip size. Thus, a user can choose different types of flash disks according to the storing requirements of different data. For example, the reliability of a flash disk has to be considered when important data is to be stored, and a memory with large storage capacity should be used for storing less important data in large quantity. However, several flash disks having different flash memories have to be carried around in order to store different data, which is very inconvenient.
Accordingly, a flash memory storage apparatus which provides multiple storage modes is desired.